Even this is flawed, because it presumes they have an understanding of the world around them; empathy, or at least perception that isn’t completely egocentric.
I think that I’m reasonably self-aware and fairly perceptive; I also think, reading this, that reasonably self-aware people rarely stop to think about “masks” and “personae” because we think of it as “situational awareness” and “appropriate behavior,” not “donning a mask” or “putting on an act.” So we’re probably the ones giving this terrible advice to people who aren’t at all capable of understanding our terms, as we mean them! Sure, we have these “masks” and “personae” as well, but they’re integrated — they are what makes us whole, and they’re not like a suit of clothes hanging in the closet that we take out for an interview. Sure, we know better than to say “Fuck it” during an interview, but that’s our situational awareness, our understanding that that’s not the time or the place. We’re not shocked or surprised that we have it in us to use four-letter words, but neither would we normally use them to attack anyone — that’s just not natural. We don’t have some “beast” lurking in the basement of our psyches, just waiting to pounce, like some Jekyll and Hyde.